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fs-util: no need for fchmod_and_chown() to access /proc/self/fd directly 

fstat(2) is fine with O_PATH fds.

For changing owership of a file opened with O_PATH, there's fchownat(2).

Only changing permissions is problematic but we introduced fchmod_opath() for
that purpose.
This commit is contained in:
Franck Bui 2019-06-06 14:05:27 +02:00
parent b337d89c68
commit 71ec74d193
1 changed files with 5 additions and 8 deletions
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13
src/basic/fs-util.c
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@ -226,7 +226,6 @@ int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
}
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
char fd_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
bool do_chown, do_chmod;
struct stat st;
@ -236,11 +235,9 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
* unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does
* on chown().
*
* This call is happy with O_PATH fds, since we always go via /proc/self/fd/ to change
* ownership/access mode. */
* This call is happy with O_PATH fds. */
xsprintf(fd_path, "/proc/self/fd/%i", fd);
if (stat(fd_path, &st) < 0)
if (fstat(fd, &st) < 0)
return -errno;
do_chown =
@ -262,16 +259,16 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */
if (((minimal ^ st.st_mode) & 07777) != 0)
if (chmod(fd_path, minimal & 07777) < 0)
if (fchmod_opath(fd, minimal & 07777) < 0)
return -errno;
}
if (do_chown)
if (chown(fd_path, uid, gid) < 0)
if (fchownat(fd, "", uid, gid, AT_EMPTY_PATH) < 0)
return -errno;
if (do_chmod)
if (chmod(fd_path, mode & 07777) < 0)
if (fchmod_opath(fd, mode & 07777) < 0)
return -errno;
return do_chown || do_chmod;